1. LGN & CORTEX
© Wesner, M. F.

2. A perceptual pathway:
Retinogeniculostriate (retina - thalamus - cortex)
V1 or striate cortex
Nonperceptual pathways:
Retinotectal (retina to superior colliculus)
Retinohypothalamic (retina - hypothalamus - pineal)

4. Retinogeniculate and retinotectal projections

5. “Retinogeniculocortical” or “retinogeniculostriate” pathway - mediates conscious visual perception

7. On-Center; Off-Surround Cell in LGN
Historic movie footage of early single-cell recording in the cat visual system by David Hubel and Torsten Wiesel.

12. contralateral
ipsilateral

13. The projections of the small ganglion (PC cells) and large ganglion (MC cells) cells to the parvocellular and magnocellular layers of the LGN:
Acknowledgement:   Image from Webvision by Kolb, Fernandez and Nelson, courtesy of Matthew Schmolesky at Erasmus University, Rotterdam.

15. This means that all information in the right (left) visual field projects to the left (right) cortex.
This means ViSUAL INFORMATION is contralaterally represented.

18. Ocular Dominance

20. This begins to establish a retinotopic organization to the cortex.

22. A recently recognized, anatomically & functionally distinct third subdivision of the visual pathway, called the koniocellular (KC) pathway.

23. The properties of koniocellular cells have only recently been studied in anthropoid primates, and their importance for human vision is only now becoming understood, particularly with respect to S-cone operations.

24. KC cells form thin layers that lie between the M and P layers
KC cells form thin layers that lie between the M and P layers..formally referred to as “intercalated layers”.

26. Generally, the spatial and temporal properties of the KC cells in primates fall between the parvocellular and magnocellular spatiotemporal properties..

27. Spatially, the KC cells are species specific
Spatially, the KC cells are species specific. Generally, however, they are tuned to spatial frequencies that are lower than the PC system but higher than the MC system.
Similarly, the temporal modulation (i.e., “timing”) sensitivity of KC cells are higher than PC but lower than MC cells.

28. The projections of the koniocellular cells to the primary visual cortex (V1) appear to be towards the cytochrome oxidase (CO) cortical blobs (i.e., cortical areas responsive to chromatic changes). KC cells are particularly responsive to “blue-yellow” differences (S-cone ON mediated).

29. The projections of the koniocellular cells to the primary visual cortex (V1) appear to be towards the cytochrome oxidase (CO) cortical blobs (i.e., cortical areas responsive to chromatic changes). KC cells are particularly responsive to “blue-yellow” differences (S-cone ON mediated). V1

30. Primary visual cortex (V1)
Brodmann 17
Striate cortex

31. The retinotopic organization of V1 (striate cortex) using 2-dg autoradiography

32. This begins to establish a retinotopic organization to the cortex.

35. Note: A retinotopic map can also be found in the superior colliculus of the mesencephalon, but more distorted than at the cortex.

37. CORTEX: Simple Cells

43. CORTEX: Complex Cells

47. CORTEX (beyond V1): Hypercomplex or End-Stop Cells ?

49. Complex Cell End-Stop Cell Slit Length (deg visual angle)

50. Possible circuit for an end-stop cell
3 converging complex cells. - +

51. V1 (primary visual cortex):
Orientation columns

52. Look at a gyrus of the primary visual cortex (Area #17) or V1 or striate cortex.

55. 2-dg treated
Orientation Columns

56. V1 (primary visual cortex):
ocular dominance columns

57. OCULAR DOMINANCE COLUMNS
PRO* treated
Radioactive proline injected into the eye.
OCULAR DOMINANCE COLUMNS

59. Margaret Wong-Riley (1979) coined the term blobs.
Introduced labeled cytochrome oxidase (an enzyme used in cellular metabolism) and measured its migration to V1. Prominent blobs found in layer III of V1 cortex.

62. Granular
Agranular

64. Six Layers of the Striate Cortex (V1): Layer devoid of nuclei
Orientation, ocular dominance columns & (inter)blobs (input from 4A & 4Cb - PARVO)
Afferent Input - big sensory layer
Input from PARVO & 4Cb
Input from 4Ca
Afferent Input
..from MAGNO (Mx & My cells)
..from PARVO (P cells: foveal chromatic & luminance signals)
Feedback to superior colliculus (visual motor)
Feedback to LGN (visual motor)
To V2 (thin stripes & pale stripes) & V4

65. ventral
dorsal
(Layers 3, 4,5, 6)

66. Six Layers of the Striate Cortex (V1): Layer devoid of nuclei
Orientation, ocular dominance columns & blobs (input from 4A & 4Cb - PARVO)
Afferent Input - big sensory layer
Input from PARVO & 4Cb
Input from 4Ca
Afferent Input
..from MAGNO (Mx & My cells)
..from PARVO (P cells: foveal chromatic & luminance signals)
Feedback to superior colliculus (visual motor)
Feedback to LGN (visual motor)
To V2 (thick stripes), V3 & MT (V5)

67. ventral
dorsal
(Layers 1,2)

68. Chromatic or luminance responsive
IVA
luminance responsive
Chromatic or luminance responsive

69. V2 (thin stipes)
interblobs
V2 (pale stipes)

70. Magno (MC) & Parvo (PC) projections
V4 (form, color, constancies)
Inferotemporal (high form)
Magno (MC) & Parvo (PC) projections
RIGHT
LEFT
RIGHT
LGN
V3 (movement, orientation, depth)
V5 (MT) (movement, dynamic form)
ipsilateral
right eye (OD)
contralateral
left eye (OS)

72. Parvocellular (PC) stream
A quick down & dirty:
Parvocellular (PC) stream
LGN Layers: 3, 4, 5, 6
V1: IVCb, IVA
V1 (layers II & III): blobs (chromatic) & interblobs (luminance) & orientation & some ocular dominance columns.
V2: thin stripes (chromatic) & pale stripes (luminance)
V4: (color, color constancy & form)
Inferotemporal: (form & color)
extrastriate

73. Koniocellular (KC) stream
A quick down & dirty (cont.):
Koniocellular (KC) stream
LGN Layers: intermediate (intercalated between all layers: 1, 2, 3, 4, 5, 6)
V1: Straight into layers II & III blobs (chromatic).
V2: thin stripes (chromatic)
V4: (color, color constancy & form) and..
V5 (MT): (motion, dynamic form)
Inferotemporal: (form & color) and..
Dorsal (movement)
extrastriate

74. Magnocellular (MC) stream
A quick down & dirty (cont.):
Magnocellular (MC) stream
LGN Layers: 1, 2
V1: IVCa, IVB
V2: thick stripes (luminance only)
V3: (motion, orientation, depth)
V5 (MT): (motion, dynamic form)
Dorsal (MST) (movement)
extrastriate

75. (Layers 3,4,5,6)

77. Extrastriate or

78. 2 major visual streams:
“WHERE” V1
#17
“WHAT”

79. Cortical damage (occipitotemporal): Apperceptive Agnosia
Cortical damage here:
Akinetopsia
Cortical damage here:
Achromatopsia
Cortical damage here:
Blindness
Cortical damage (occipitotemporal):
Apperceptive Agnosia
Cortical damage (fusiform gyrus):
Apperceptive Prosopagnosia

81. Do sensory pathways always involve such anatomical divisions of labor?
Multisensory operations generally occur at high-level associative cortical sites in the processing heirarchy.
Do sensory pathways always involve such anatomical divisions of labor? NO

82. Modular processing
The general cortical architecture of sensory processing, according to the modularity theory. Specialized processing systems are dedicated to different sensory modalities; vision (red), audition (blue), and somatosensation (green). In each system information flow divides into two streams, one carrying “what” information and the other carrying “where” information. Multisensory processing occurs relatively late in the processing hierarchy, in the intraparietal sulcus (IP) and the superior temporal polysensory area (STP), both shown in multiple colors. Re-drawn from Schroeder, Smiley, Fu, McGinnis, O’Connell, and Hackett (2003), Figure 1. Copyright © Elsevier. Reproduced with permission.

83. Modular processing
Modular processing architecture has a number of virtues.
For example, each module can be optimized for its specific function, operating with maximum speed and efficiency rather than compromised to serve several functions at once.
Errors remain confined to one function, rather the propagated widely.
New functions can be created by adding new modules.